perf(move-file): intern common path strings

[LayZeeDK]

Summary

Introduce string interning for frequently reused path values inside the move-file generator caches.

Proposed Solution

const stringInternCache = new Map<string, string>();

function intern(str: string): string {
  let interned = stringInternCache.get(str);
  if (interned === undefined) {
    interned = str;
    stringInternCache.set(str, interned);
  }
  return interned;
}

function getProjectSourceFiles(tree: Tree, projectRoot: string): string[] {
  const internedRoot = intern(projectRoot);
  const cached = projectSourceFilesCache.get(internedRoot);
  // ...
}

• Reuse interned strings when storing paths in caches.
• Clear the interning cache each run to keep memory bounded.

Tasks

• Add a simple string interning helper shared across caches
• Apply interning when storing/retrieving paths in hot caches (e.g. project source files)
• Ensure caches are cleared each run to avoid uncontrolled growth

Definition of Done

• Existing benchmark and stress test suites are run before and after the change; report the data in the PR description. This is mandatory.
• Unit/e2e tests continue to pass.
• Document the interning rationale where appropriate.